The Metropolitan Police Department requested the nation's retailers and beverage makers on Friday to tighten security in the wake of a recent series of poisoning cases in Wakayama, Niigata and Nagano prefectures.
The MPD issued the warning to discourage the possibility of copycat crimes, adding that similar incidents are likely to happen.
The written request, issued to seven industry organizations including national associations of supermarket operators, soft drink bottlers and vending machine makers, urges member firms to promptly report suspicious objects or people seen around their shops and factories, and to install video cameras at their facilities.
A poisoning case this week in which a resident of Obuse, Nagano Prefecture, was killed after drinking tainted tea is one of a recent spate of unresolved poisonings that has shaken the nation over the past two months.
In July, four people died and 63 became ill after eating arsenic-laced curry served at a summer festival in Wakayama. Last month, 10 workers of the Niigata branch office of a wood preservative company were hospitalized after drinking tea and coffee laced with sodium azide.
Alarmed by the incident, a national association of soft drink makers held an emergency meeting in Tokyo on Friday to discuss preventive measures.
The participants agreed to put stickers on about 2 million soft drink vending machines nationwide urging purchasers to look for irregularities in the containers and to be on guard for any drinks that may have been left inside the dispensing areas.